arm A: neoadjuvant chemotherapy + resection + adjuvant chemotherapy arm B: resection + adjuvant chemotherapy Neoadjuvant chemotherapy consists of gemcitabine (1000mg/m2) and oxaliplatin (100mg/m2) on days 1, 15, 29 and 43, while adjuvant chemotherapy is based on gemcitabine 1000mg/m2 for 6 months.